1. Field of the Invention
The invention relates generally to wireless communications and more specifically to a system and method of concurrent wireless voice and data communications.
2. Description of Related Art
The following background information is provided to aid in the understanding of the application of the present invention and is not meant to be limiting to the specific examples set forth herein. Reference is made to FIG. 1 that depicts the prior art Digital Enhanced Cordless Telecommunications (DECT) standard protocol promulgated by the European Telecommunications Standards Institute (ESTI). The DECT standard defines a multiple carrier, time-division-multiple-access (TDMA), time-division-duplex (TDD) protocol with ten channels (carrier frequencies) between 1881.792 MHz and 1897.344 MHz spaced 1.728 MHz apart. Each of the ten channels supports a ten-millisecond frame comprised of twenty-four time slots. TDD is provided by allocating twelve of the twenty-four slots for base station to cordless handset communications and the other twelve slots for cordless handset to base station communications. Each time slot comprises 480 bits with a 32-bit preamble for synchronization, 388 bits for data and 60 bits for guard time. The 388 data bits are further divided into an A-field, a B-field and 4 parity bits for error detection. The A-field comprises an 8-bit header, 40 bits of control information and 16 cyclic redundancy check (CRC) bits while the B-field provides 320 bits of data.
For speech applications, analog signals are digitized and encoded using adaptive differential pulse code modulation (ADPCM). So-called “frequency hopping” is employed to avoid interference by periodically assigning a different one of the ten channel frequencies to each of the twenty-four time slots. A form of frequency shift keying known as Gaussian filtered, Minimum Shift Keying (GMSK) is used to modulate the transmitted signal to provide continuous phase transitions between two adjacent symbols.
By way of further background circa 1992, the Olivetti corporation released a DECT-based wireless local area network (LAN) data communication product known as “NET3”. Thereafter, the Siemens corporation introduced a voice communication DECT-based product known as the “Gigaset 900”. Subsequent to and on going, ETSI promulgated a range of Radio local loop Access Profiles (RAP) to designate DECT standard interoperability with products employing the so-called wireless local loop (WLL) a.k.a. radio local loop (RLL) such as ISDN and GSM networks. For example, DECT is being applied to cordless terminal mobility (CTM) in Italy wherein a cordless handset operates with both private and public DECT base stations.
By way of even further background, the IEEE promulgated in its 802.11 standard, inter alia, definitions for Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Spectrum (DSSS) implementations of the physical layer of a WLAN. For FHSS in North America and most of Europe, IEEE 802.11 requires 79 channels in 1 MHz steps beginning at 2.402 GHz and ending at 2.480 GHz with a minimum frequency hop of 6 MHz. FIG. 9 depicts the IEEE 802.11 protocol for packetizing information in a FHSS WLAN. One-hundred-twenty-eight (128) bits (a 96 bit preamble and 32 bit header) are sent to assist in synchronizing after a carrier hops from one frequency to the next. Payload data then follows in sizes ranging from 1 to 4095 bytes. The IEEE 802.11 standard however is devoid of any voice communication support.
Heretofore there has not been a product that supports both voice and data communications over a wireless transmission protocol such that voice conversations and data communications take place concurrently with unitary transceiving units for supporting both types of communications.
From the foregoing it can be seen that there is a need for a system and method that supports concurrent voice and data communications over wireless radio access technology such as, but not limited to DECT, employing unitary transceiving units.